Electrochemical and microbiological insights into the use of 1,4-diazabicyclo[2.2.2]octane-functionalized anion exchange membrane in microbial fuel cell: A benchmarking study with Nafion

Abstract

In this work, two polymeric membrane separators (a proton exchange membrane (PEM), Nafion, and an anion-exchange membrane (AEM), 1,4-diazabicyclo[2.2.2]octane (DABCO)-functionalized PSEBS) deployed in microbial fuel cells (MFCs) are comparatively assessed. The performances of MFCs according to membrane type were evaluated by biological and electrochemical techniques, employing metagenomics, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). It was found that the anodic biofilms of MFCs, irrespective of the type of membrane, were dominated by Geobacter sulfurreducens (37 and 50% for AEM-MFC and PEM-MFC, respectively), a well-known electrochemically active species. Furthermore, the AEM-MFC reflected a significantly lower internal resistance (145 Ω) compared to PEM-MFC (339 Ω) and produced higher maximal current densities and energy yields at all substrate (acetate) concentrations, as follows: 400 vs. 285 mA m−2 (5 mM acetate); 360 vs. 320 mA m−2 (10 mM acetate), 305 vs. 235 mA m−2 (15 mM acetate) and 238 vs.132 kJ m−2 gCOD (5 mM acetate), 161 vs. 128 kJ m−2 gCOD (10 mM acetate), 114 vs. 59 kJ m−2 gCOD (15 mM acetate) respectively. The CV measurements implied diffusion limitations in the MFCs, which were supported by EIS. In addition, the PEM and AEM characterizations revealed that in both cases, the ion exchange capacity, ionic conductivity and oxygen mass transport features were altered considerably over the 39 days during which the MFCs operated.